Glass sheet processing systems such as the type disclosed by U.S. Pat. No. 4,575,390 include bending apparatus having one or more molds adapted to be positioned within a heating chamber and receive a heated glass sheet from a roller conveyor in preparation for tempering and/or bending.
Briefly, the glass processing system typically includes a furnace defining a heating chamber through which glass sheets are conveyed for heating in preparation for bending. The bending apparatus of the preferred system includes a roller conveyor for supplying heated glass to one or more curved molds. The curved molds are each typically mounted for movement along a single axis, and typically take the shape of a surface having a complex curvature that is generally convex in nature (mold) or a complimentary concave surface in the form of an open center ring (ring). The heated glass is formed by placing the sheet in a series of on a mold and moving the mold(s) relative to the glass to provide an accurately formed curvature according to a preselected design.
Relatively quick and accurate positioning of the curved molds during various stages of the bending and tempering process is an important factor in achieving a high quality product.
The travel of the mold and rings is typically restricted by electro-mechanical limit switches These limit switches are activated when the shuttle upon which the mold or ring is mounted contacts or passes the limit switch, resulting in immediate cutoff of the power to the drive for that shuttle. These limit switches are an important feature because they avoid the potential damage that might occur if one of the relatively large mold or ring shuttles were to exceed its desired travel limits. However, one disadvantage of limit switches is that, once mounted on the machine, the travel limits of a particular mold or ring cannot be changed unless the limit switches are moved. Also, the limit switches and associated hardware are relatively costly items.